Cellular urethanes and process for preparing same wherein a combination of stannous and lead salts are employed



United States Patent 3,385,807 CELLULAR WETHANES AND PROCESS FOR PRE-PARING SAME WHEREIN A COMBINATION 0F STANNUUS AND LEAD SALTS AREEMPLOYED Richard J. Herdlein, Buffalo, and Andrew Shultz, Williamsville,N.Y., assignors to Allied Chemical Corporation, New York, N.Y., acorporation of New York No Drawing. Continuation-impart of applicationSer. No. 414,903, Nov. 30, 1964. This application Nov. 5, 1965, Ser. No.506,577

12 Claims. (Cl. 260-25) This application is a continuation-in-part ofour 00- pending application S.N. 414,903, filed Nov. 30, 1964, and nowabandoned. This invention relates to cellular urethanes. Moreparticularly it relates to flexible cellular urethanes which possessexcellent and uniform physical properties.

Cellular urethanes are prepared by reacting, in the presence of ablowing agent, polyisocyanates with active hydrogen containingsubstances such as polyesters, including polyester amides, and hydroxylcontaining polyethers, including polyether diols and triols. Usually thereaction is carried out in the presence of catalysts such as organo-tincompounds and tertiary amines and emulsifiers such as silicone oils.These substances are incorporated in the reaction mass to controlreaction rate, cell size, porosity and the like. The urethanes aregenerally cast as slabstock on a moving belt in forms, which are open atthe top to permit free rise of the expanding polymerizing mass. As theurethane polymer rises, the material gels and the cell structure forms.Heat resulting from the several reaction-s taking place, is dissipatedat different rates throughout the polymer mass with the result that thecenter portion of the cellular product is often somewhat hotter than thetop or sides. In extreme cases, burnout can occur, i.e., the temperaturecan attain so high a degree as to cause decomposition of the polymer.More often this problem of heat transfer causes variation in thestrength and structure of the polymer slab. Such variations areundesirable since sections, taken both transversely and horizontally,show variations in physical properties to such a degree that allsections cannot be used for the same products and must be graded andsorted, an expensive and undesirable process. Certain of the sections,which fail to meet specifications, may be ground or discarded. In themanufacture of flexible cellular urethanes, which are used to a largeextent for comfort cushioning, the load bearing characteristic is animportant specification. Relatively minor variation, i.e., a differenceof more than about five pounds in load bearing as measured byindentation load deflection test (ASTM D156459T) is undesirable. Suchvariations in the load bearing characteristic of sections of flexiblecellular urethanes from top to bot-tom of the slabstock are not unusual,and are especially noted in slabstock made under conditions of highhumidity, i.e., above about 80% relative humidity, and high ambienttemperature, i.e., above about 80 F. Inasmuch as such severe conditionsprevail in many areas, where the flexible cellular urethanes aremanufactured, e.g., the southeastern United States, it can readily beseen that the manufacture of flexible cellular urethanes leavessomething to be desired.

It is, therefore, a principal object of the present invention to provideimproved cellular urethanes characterized by a minimum variance in loadbearing property throughout the cellular structure.

Another object is to devise a process for the production of cellularurethanes having substantially uniform load bearing character throughthe cellular structure.

Other objects and advantages wil1=be apparent from the followingdescription of our invention.

3,385,807 Patented May 28, 1968 I have made the surprising discoverythat flexible cellular urethane foams having an ILD (Indentation LoadDeflection) at 25% which does not vary by more than 5 pounds at anypoint can be obtained by a one-shot process comprising admixing thefollowing materials:

(a) a diisocyan-ate;

(b) a polyether polyol;

(c) water;

(d) an organic tin compound catalyst in an amount of about 1200 to about3800 parts by weight per million (ppm) parts by weight of polyetherpolyol; and

(e) a load conforming agent consisting essentially of trace amounts of alead salt of an organic acid, said lead salt being present in an amountproviding about 10 to about parts by weight of lead per million parts byweight of polyether polyol.

It is most important in order to obtain the esired result of the presentinvention to keep the lead content within the prescribed range and tosimultaneously maintain the organic tln catalyst within its prescribedrange. It is not understood why the tin catalyst must be limited withinthe conventional range-s, but it has been observed in numerous teststhat a material departure from prescribed proportions of tin and leadcompounds results in impairment of the properties of the urethane foam.

The resultant cellular urethane structures are characterized by havingsubstantially uniform load bearing characteristics, i.e., theindentation load deflection at 25% deflection of a section taken at anypoint of the cellular structure does not vary by more than five poundsfrom that of a section taken from another part of the said structure.

Such uniformity of the load bearing characteristic of the cellularstructure enables the production of urethanes with a minimum of waste,and thus improves the economics of the manufacture of this type ofmaterial.

The polyether polyols used in this process include those of the flexibletype. Such compounds are known in this art and are believed to haveessentially the following general formula:

wherein R is the residue of a polyol as exemplified below; R is hydrogenor methyl; A is hydrogen, CH CH OH, or CH CH CH OH, x is an integer from5 to 50, y is an integer 2 or 3, and z is an integer 0 or 1. Suchpolyether polyols can be obtained in a known manner by condensation ofalkylene oxide such as ethylene oxide, 1,2-prropylene oxide,1,3-propylene oxide or mixtures thereof with polyhydric alcohols, suchas ethylene glycol, propylene glycol, dipropylene glycol, tetramethyleneglycol, glycerin, trimethylol propane or mixtures thereof, in thepresence of suitable catalysts or initiators such as trialkylamines,e.g., trimethylamine, or inorganic bases, e.g., potassium .hydroxide, ora halide, e.g., boron trifluoride. Those products resulting from thecondensation of 1,2-propylene oxide and mixtures thereof with ethyleneoxide are preferred. The molecular weights of the polyether polyolspreferably range from about 400 to about 6000.

Polyether polyols prepared from ethylene oxide and a glycol or triol maybe used but such products are soluble in water to a significant extentand the polymers derived therefrom are characterized by poor hydrolyticstability.

In an especially preferred embodiment, we employ a more reactive polyol,an ethylene oxide capped or tipped polyether polyol such as an ethyleneoxide tipped glycerine initiated polyoxypropylene triol having ahydroxyl number of 46 and a primary hydroxyl group content of about 35%.We have found that flexible cellular urethanes utilizing these morereactive polyols having primary hydroxyl groups require a significantlysmaller amount of lead. These reactive polyols, referred to hereafter astipped polyether polyols, and their preparation are well-known in theart as illustrated by US. Patent 3,016,404.

A general discussion of polyether polyols and their preparation can befound in Saunders et al., Polyurethanes, Chemistry and Technology, pt.I, Chemistry, High Polymers, vol. XVI, Interscience Publishers, 1962,pp. 32-44 and pt. I, p. 5.

Any of a wide variety of diisocyanates, or mixtures thereof, can be usedin this novel process. Liquid diisocyanates are preferred. As examplesof this component, the following are mentioned: m-phenylenediisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,naphthalene-1,S-diisocyanate, naphthalene 1,8 diisocyanate,4,4-methylene-bis- (phenylisocyanate) 4,4'-methylene-bis(tolylisocyanate), 4,4'-methylene bis(cyclohexylisocyanate),i,6-hexamethylene diisocyanate.

A general discussion of isocyanates and their preparation can be foundin Saunders et al., cited supra, pp. 17-32.

Tolylene diisocyanates such as those disclosed in French Patent No.1,375,975 are contemplated.

The amount of diisocyanate used is generally sufficient to react withthe hydroxyl groups of the polyol and with the water used to generatecarbon dioxide for blowing the mixture. Preferably an amount ofpolyisocyanate is used which is sufiicient to provide a ratio of NCO toactive hydrogens within the range of 0.9 to 1.5 :1. Especially preferredis the use of an NCO:H ratio of 1.0 to 1.221.

In accordance with what is now conventional practice for producingflexible cellular urethane structures, the polyisocyanate-polyol mixturemay be reacted in the presence of various adjuvants such as auxiliaryblowing agents, activators and/or catalysts, dispersing agents oremulsifiers and the like.

The improved cellular urethanes of our invention are primarilywater-blown structures. Water by reaction with the isocyanate componentgenerates carbon dioxide gas for the blowing and additionally forms ureagroups which are believed to contribute to chain stiifeners andstability under humid aging conditions. Urea groups, on the other hand,induce hardness in the cellular structure. Auxiliary blowing agents,particularly non-reactive low boiling organic liquids, may be used toincrease softness and decrease density in such products. Such liquids asmethylene chloride and particularly fluorin-ated hydrocarbons as well asmixtures thereof can be used.

The amount of water supplied may be sufiicient to generate all the COnecessary or may be employed in lesser amount and supplemented by anauxiliary blowing agent, as noted. The amount of water can vary fromabout 1 part to 6 parts per 100 parts by weight of the polyol,preferably, about 2 to about 4 parts per 100 parts of polyol.

Such agents are characterized by being liquids or gases at normaltemperatures and pressures, poor solvents for the organic polymer and byboiling at temperatures at or below that generated by the urethaneformation reaction. The last characteristic is useful as it provides ameans of reducing heat build up in the polymer forming mass. Increasingthe concentration of these auxiliary agents decreases the maximumtemperature Within the cellular structure and increases the time toreach this maximum temperature. As typical examples of thesefluorocarbons the following are mentioned: monofluorotrichloromethane;dichlorodifiuoromethane; monochlorotrifluoromethane;trichlorotrifluoroethane; dichlorotetrafiuoroethane;difluorotetrachloroethane; 1,1 difluoroethane;1,1,1-dichlorofluoroethane.

Mixtures of these and equivalent auxiliary blowing agents arecontemplated also.

Conventional organo-tin salt catalysts can be used. The preferredorgano-tin salt catalysts are exemplified by stannous octoate andstannous oleate. The organo-tin salt catalyst must be present in amountsfrom about 1200 to about 3800 p.p.m. based on the weight of the polyol.In general, for each p.p.m. of lead employed, about 10. p.p.m. less ofthe tin catalyst should be employed. Thus when employing the tippedpolyether polyols, from about 1900 to about 2900 p.p.m., preferablyabout 2200 to about 2750 p.p.m. are employed. When employing the moreconventional polyether polyols, from about 1250 to about 2500 p.p.m.,preferably about 1800 to about 2300 p.p.m. are employed.

Auxiliary catalyst such as the tertiary amine catalysts are preferablyused in addition to the organo-tin compound. Examples of tertiary aminecatalysts are: triethylamine, N-methylmorpholine, triethylenediamine,N,N,N, N, tetramethyl-1,3-butanediamine, and soya lecithin.

Trace amounts of a load conforming agent are necessary to this process.The load conforming agent of this invention consists essentially of alead salt of an organic acid. These lead salts are preferably soluble inthe polyether polyol. The organic acid portion of the lead salt can be asaturated or unsaturated, straight or branched chain, aliphatic orcycloaliphatic carboxylic acid. The number of carbons can range from 5to 30 or more. Aryl carboxylic acids are also satisfactory. Thecompounds can be substituted or unsubstituted, but are preferablyhydrocarbons with one carboxyl group although more than one carboxylgroup can be present. Typical compounds are lead-2-ethylhexoate, leadoleate, lead stearate, lead ricinoleate, lead palmitate, leadnaphthenate and lead benzoate. The preferred salt is lead-Z-ethylhexoatebecause of its superior activitiy and ready availability.

The amount of lead salt must be present in an amount providing about 10to about 175 p.p.m. by weight of lead based on the polyether polyol.When employing the tipped polyether polyols, lower amounts of lead maybe employed in the range of about 10 to about p.p.m., preferably 25 to80 p.p.m. and when employing the more conventional polyether polyols,amounts from about 70 to about 175 p.p.m., preferably 70 to p.p.m. areemployed. It is preferred to use a higher amount of lead salt with alower amount of tin salt or a lower amount of lead salt with a higheramount of tin salt within the prescribed ranges.

Dispersing or emulsifying agents conventionally used in this art includepolyethylene phenol ethers, blends of polyalcohol carboxylic acidesters, oil soluble sulfonates, siloxane-oxyalkylene block co-polymersand the like. The preferred adjuvants of this group in the presentinstance are the silicone-oxyalkylene block co-polymers, having thegeneral formula:

wherein R, R, and R" are C alkyl radicals; p, q and r are integers from2 to 15, and ----(C,,H O) is a. polyoxyalkylene block which ispreferably a polyoxyethylene containin from 10 to 50 of eachpolyoxyalkylene unit. Products of this type are disclosed in U.S.P.2,834,748 and Belgium Patents 582,362-3. Such siloxane-oxy-alkyleneblock copolymers are available commercially, one such product beingoffered in which above general formula R=CH R=C H R"=C H p=q=r=7, andthe block, --(C,,H ,,,O) is a polyoxyethylene-polyoxypropylene blockcontaining about 50 units of each polyoxyalkylene moiety.

The formulation, curing and application treatments of cellular urethanestructures of this general class to which the novel compositions of thisinvention belong are well known to those skilled in the art to whichthese novel compositions pertain and accordingly no extended discussionof these well-known and conventional collateral aspects of theinventions is deemed necessary.

As indicated above, the problem of variance. in load bearing characterof cellular urethanes may be due, in part, to differences in heattransfer and rate of polymer growth which occurs during the polymerforming reaction. As the size of the polymer product increases thesevariations will be intensified. The problem is of minor consequence inlaboratory prepared cellular structures wherein the polymer structurerarely exceeds 12 inches in height. Present day commercial practicewherein cellular structures are produced on endless belts generallyreach the size of 36 or more inches in width, 14 or more inches inheight and have a length of to or more feet. In such commerciallyproduced blocks or buns the temperature of the outer and mid portionsmay vary 100 F. or more due to the low thermal conductivity of theurethane polymer. Such large temperature variations, it is believed, areaccompanied by variations in polymer growth and curing which doubtlesslyresult, to a major extent, in the variation in physical properties,notably load bearing. Thus as the dimensions of the bun increase thevalue of the present invention increases also.

The more detailed practice of the present invention will be illustratedby the following examples in which parts and percentages are by weightand temperatures are given in degrees centigrade.

EXAMPLE 1 A solution of 0.031 part of Iead-Z-ethyl hexoate in 100 partsof a glycerin initiated polyoxypropylene triol having an averagemolecular weight of 3000 was prepared. The solution contained 130 p.p.m.of lead. To this solution the following were added:

3.9 parts of water 0.1 part triethylenediamine 1.3 partsiloxane-oxyalkylene block copolymer, and 0.20 part of stannous octoate.

The resulting mixture was thoroughly mixed and then combined with 48.7parts of a mixture of about 80% 2,4-tolylene diisocyanate and about2,6-tolylene diisocyanate in a conventional slabstock machine operatingat the rate of about 250 lbs/min. The buns, which rose to a height ofabout 26 inches were permitted to stand at ambient temperature for about16 hours (over night). Thereafter sections taken at 4 in. intervals fromthe top to the bottom of the slab or bum were submitted to theIndentation Load Deflection (ILD) Test at deflection. The resultsobtained are given in Table 1 below.

EXAMPLE 2 The procedure of Example 1 above was repeated with theexception that the stannous octoate was increased to 0.24 part insteadof 0.20 part. The ILD values, determined in an analogous fashion, arealso set out in Table 1 below.

EXAMPLE 3 The procedure of Example 1 was again repeated and the leadoctoate was omitted. Additional tin salt was added to compensate for thelead octoate. The ILD values are set out in Table 1 below.

TABLE 1.-INDENTATION LOAD DEFLECTION AT 25% These data indicate that thebun prepared in Examples 2 and 3 would not be satisfactory due to thedifference in load bearing character from top to bottom. The top 4 inchsection would have to be removed and regraded to a lower classification,or shredded to be used as filler or scrapped. However, the bun preparedin Example 1 is satisfactory from top to bottom and only the skin needsto be removed.

The following flexible cellular foams were prepared employing theprocedure of Example 1, differing therefrom in 1) the polyols used; (2)the amounts of lead; (3) the amounts of tin catalyst.

Foam A To a polyol blend composed of:

(1) 60 parts of an ethylene oxide tipped glycerine initi atedpolyoxypropylene triol having an OH No. (hydroxyl number) of 46 and aprimary hydroxyl group content of about 35%,

(2) 20 parts of a glycerine initiated polyoxypropylene triol having anOH No. of 56 containing essentially all secondary hydroxyl groups, and

(3) 20 parts of a polyoxypropylene diol having an OH No. of 56.

Lead octoate was added in sufiicient amount to provide 60 parts of leadper million parts of polyol. The resulting solution was reacted in aconventional slabstock foaming equipment with the following:

3.75 parts of water 0.13 part of triethylene diamine 1.35 partssiloxane-oxyalkylene block copolymer 0.33 part stannous octoate 4.0parts methylene chloride 45.2 parts tolylene diisocyanates The resultingbuns were permitted to stand at ambient temperature for about 16 hours(overnight). Sections of the resultant foam slab taken at approximate 4in. intervals from top to bottom were submitted to the ILD test at 25%deflection. The results obtained did not vary more than 2.7 lbs.

Foam B Foam B was prepared as Foam A except for the following:

Foam C was prepared as described for Foam B with the exception that theproportion of stannous octoate was increased to 0.33 part. The resultantfoam showed a variation of 2 lbs. from top to bottom in ILD at 25deflection.

Foams D, E and F Foams D, E and F were prepared as described for Foam Cwith the following differences:

(1) The triol used was an ethylene oxide tipped glycerine initiatedpolyoxypropylene triol from a different batch having a primary hydroxycontent of about 37.5%.

(2) The triol/diol blend in each of these three instances contained 25p.p.m. of lead.

(3) The stannous octoate was varied from 0.24 part in Foam D, to 0.27part in Foam E, to 0.33 part in Foam F.

Foam D showed a variance of 2.2 lbs. Foam E showed a variance of 1.9lbs. Foam F showed a variance of 4.0 lbs.

It can thus be seen that an effective means for improving the uniformitywith respect to load bearing character of cellular urethanes has beendevised. By this means, the manufacture of such foams can be carried.out Without the frequent and troublesome necessity of cutting away anddiscarding those portions of the non-uniform buns which did not meet therequired specification, a problem which high humidity and high ambienttemperature apparently intensifies.

We claim:

1. A one-shot process for preparing flexible cellular urethane foamscomprising admixing:

(a) organic diisocyanate;

(b) a polyether polyol;

() water;

((1) an organic-tin catalyst selected from the group consisting ofstannous oleate and stannous octoate in an amount of about 1200 to about3800 parts by weight per million parts by weight of polyether polyol;and

(e) a load conforming agent consisting essentially of trace amounts of alead salt of an organic carboxylic acid of to 30 carbon atoms, said leadsalt being present in an amount providing about to about 175 parts byweight of lead per million parts by weight of polyether polyol with theproviso that when more than about 2300 parts by weight of said organictin compound and less than about 70 parts by Weight of said lead permillion parts by weight of said polyether polyol is used, said polyetherpolyol is an ethylene oxide tipped polyether polyol.

2. The process of claim 1 wherein said polyether polyol is selected fromthe class represented by the general formula:

i zlil z h ly 0H, R1

wherein R is the residue of an alkylene polyol;

R is hydrogen or methyl;

A is hydrogen, CH CH OH .or -CH CH CH OH; x is an integer from 5 to 50;

y is the integer 2 or 3; and

z is the integer 0 or 1.

3. The process of claim 2 wherein said organic tin catalyst is presentin an amount of about 1250 to about 2300 parts by weight per millionparts by weight of polyether polyol and said lead salt is present in anamount providing about 70 to about 175 parts by weight of lead permillion parts by weight of polyether polyol.

4. The process of claim 2 wherein said organic tin catalyst is presentin an amount of about 1800 to about 2300 parts by weight per millionparts by weight of polyether polyol and said lead salt is present in anamount providing about 70 to about 120 parts by weight of lead permillion parts by Weight of polyether polyol.

5. The process of claim 1 wherein said polyether polyol is an ethyleneoxide tipped polyether polyol.

6. The process of claim 5 wherein said organic tin catalyst is presentin an amount of about 1900 to about 2900 parts by Weight per millionparts by weight of polyether polyol and said lead salt is present in anamount providing about 10 to about 110 parts by weight of lead permillion parts by weight of polyether polyol.

7. The process of claim 5 wherein said organic tin catalyst is presentin an amount of about 2200 to about 2750 parts by weight per millionparts by weight of polyether polyol and said lead salt is present in anamount providing about 25 to about parts by weight of lead per millionparts by weight of polyether polyol.

8. The product produced by the process of claim 1.

9. The process of claim 1 wherein said amount of said tin catalyst andsaid amount of said lead salt are used so that a lower amount of tincatalyst is employed with a higher amount of lead salt and a higheramount of tin catalyst is employed with a lower amount of lead salt.

10. The process of claim 1 wherein said polyether polyol is an ethyleneoxide tipped glycerine initiated polyoxypropylene trio] and wherein saidorganic tin catalyst is present in an amount of about 1900 to about 2900parts by weight per million parts by weight of polyether polyol and saidlead salt is present in an amount providing about 10 to about parts byweight of lead.

11. A one-shot process for preparing flexible cellular urethane foamscomprising admixing:

(a) organic diisocyanate;

(b) a polyether polyol;

(c) water;

((1) an organic tin catalyst selected from the group consisting ofstannous oleate and stannous octoate in an amount of about 1200 to about3800 parts by weight per million parts by weight of polyether polyol;and

(e) a load conforming agent consisting essentially of trace amounts of alead salt of an organic carboxylic acid selected from the groupconsisting of lead octoate, lead oleate, lead stearate, leadricinoleate, lead palmitate, lead naphthenate and lead benzoate, saidlead salt being present in an amount providing about 10 to about partsby weight of lead per million parts by weight of polyether polyol withthe proviso that when more than about 2300 parts by weight of saidorganic tin compound and less than about 70 parts by weight .of saidlead per million parts by weight of said polyether polyol is used, saidpolyether polyol is an ethylene oxide tipped polyether polyol.

12. The process of claim 11 wherein said tin catalyst is selected fromthe group consisting of stannous octoate and stannous oleate and whereinsaid lead salt is lead octoate.

References Cited UNITED STATES PATENTS 3,267,047 8/1966 Gmitter et al260-25 3,039,976 6/1962 Barnes 260-25 3,127,312 3/1964 Boyer 260-253,179,627 4/ 1965 Twitchett 260-45 .75 3,182,037 5/1965 Nelson 260-45753,238,273 3/ 1966 Hampson et al. 260-25 3,245,923 4/1966 Manzella et al.260-25 DONALD E. CZAIA, Primary Examiner.

MICHAEL B. FEIN, Assistant Examiner.

1. A ONE-SHOT PROCESS FOR PREPARING FLEXIBLE CELLULAR URETHANE FOAMSCOMPRISING ADMIXING: (A) ORGANIC DIISOCYANATE; (B) A POLLYETHER POLYOL;(C) WATER; (D) AN ORGANIC-TIN CATALYST SELECTED FROM THE GROUPCONSISTING OF STANNOUS OLEATE AND STANNOUS OCTOATE IN AN AMOUNT OF ABOUT1200 TO ABOUT 3800 PARTS BY WEIGHT PER MILLION PARTS BY WEIGHT OFPOLYETHER POLYOL; AND (E) A LOAD CONFORMING AGENT CONSISTING ESSENTIALLYOF TRACE AMOUNTS OF A LEAD SALT OF AN ORGANIC CARBOXYLIC ACID OF 5 TO 30CARBON ATOMS, SAID LEAD SALT BEING PRESENT IN AN AMOUNT PROVIDING ABOUT10 TO ABOUT 175 PARTS BY WEIGTH OF LEAD PER MILLION PARTS BY WEIGHT OFPOLYETHER POLYOL WITH THE PROVISO THAT WHEN MORE THAN ABOUT 2300 PARTSBY WEIGHT OF SAID ORGANIC TIN COMPOUND AND LESS THAN AOUT 70 PARTS BYWEIGHT OF SAID LEAD PER MILLION PARTS BY WEIGHT OF SAID POLYETHER POLYOLIS USED, SAID POLYETHER POLYOL IS AN ETHYLENE OXIDE TIPPED POLYETHERPOLYOL